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101.
Alessandra?CellettiEmail author Letizia?Stefanelli Elena?Lega Claude?Froeschlé 《Celestial Mechanics and Dynamical Astronomy》2011,109(3):265-284
We perform an analysis of the dynamics of the circular, restricted, planar three-body problem under the effect of different
kinds of dissipation (linear, Stokes and Poynting–Robertson drags). Since the problem is singular, we implement a regularization
technique in the style of Levi–Civita. The effect of the dissipation is often to decrease the semi-major axis; as a consequence
the minor body collides with one of the primaries. In general, it is quite difficult to find non-collision orbits using random
initial conditions. However, by means of the computation of the Fast Lyapunov Indicators (FLI), we obtain a global view of
the dynamics. Precisely, we detect the regions of the phase space potentially belonging to basins of attraction. This investigation
provides information on the different regions of the phase space, showing both collision and non-collision trajectories. Moreover,
we find periodic orbit attractors for the case of linear and Stokes drags, while in the case of the Poynting–Robertson effect
no other attractors are found beside the primaries, unless a fourth body is added to counterbalance the dissipative effect. 相似文献
102.
Francesco Mastrototaro Porzia Maiorano Agostina Vertino Daniela Battista Antonella Indennidate Alessandra Savini Angelo Tursi Gianfranco D'Onghia 《Marine Ecology》2013,34(3):313-320
During a research cruise carried out in April 2010, aimed at updating the knowledge on the biodiversity of the Santa Maria di Leuca (SML) cold‐water coral province (Mediterranean Sea), a facies of the sea pen Kophobelemnon stelliferum (Muller, 1776) was found on mud‐dominated bottoms. This finding represents a new species and a new habitat record from the SML coral province as well as a new bathyal facies in the whole Central Mediterranean Sea. The colonies were collected using an epi‐benthic sledge, at depths between 400 and 470 m. A significant positive relationship between polyp number and colony length was detected. Density of the colonies ranged from 0.003 to 0.038 N·m?2. Differences and affinities between Mediterranean and Atlantic occurrences of K. stelliferum are discussed. 相似文献
103.
Alessandra Celletti George Voyatzis 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):101-113
We investigate the rotational dynamics of a triaxial planet moving on a Keplerian orbit around its star. The dynamics is ruled by several parameters, like the eccentricity, the obliquity, the non-principal rotation, the angular momentum, etc. We consider two specific cases in which the planet is symmetric or asymmetric, according to whether two moments of inertia coincide or differs from each other. We study the dynamics by constructing maps of dynamical stability based on the computation of the maximum Lyapunov characteristic number versus some typical parameters. The results show that only specific resonances appear in the symmetric case, while the asymmetric case shows a much richer phenomenology. 相似文献
104.
Flooding scenarios due to land subsidence and sea‐level rise: a case study for Lipari Island (Italy)
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Marco Anzidei Alessandro Bosman Roberto Carluccio Daniele Casalbore Francesca D'Ajello Caracciolo Alessandra Esposito Iacopo Nicolosi Grazia Pietrantonio Antonio Vecchio Cosmo Carmisciano Massimo Chiappini Francesco Latino Chiocci Filippo Muccini Vincenzo Sepe 《地学学报》2017,29(1):44-51
Archaeological and instrumental data indicate that the southern sector of the volcanic island of Lipari has been subsiding for the last 2100 years due to isostatic and tectonic factors, at variable rates of up to ~11 mm a?1. Based on this data, a detailed marine flooding scenario for 2100 AD is provided for the bay of Marina Lunga in the eastern part of the island from (1) an ultra‐high‐resolution Digital Terrain and Marine Model (DTMM) generated from multibeam bathymetry (MB) and Unmanned Aerial Vehicles (UAV), (2) the rate of land subsidence from Global Positioning System (GPS) data and (3) the regional sea‐level projections of the International Panel on Climate Change (IPCC). When land subsidence is considered, the upper bound of sea‐level rise is estimated at 1.36 m and 1.60 m for RCP4.5 and RCP8.5 climate change scenarios, respectively. Here, we show the expected impact of marine flooding at Lipari for the next 85 years and discuss the hazard implications for the population living along the shore. 相似文献
105.
Maria Teresa Giugliano Alessandra Longo Rosario Montuori Vincenzo Piluso 《地震工程与结构动力学》2011,40(13):1455-1474
Structural engineering problems are always affected by many sources of uncertainty, such as aleatory of material properties, applied loads and earthquake intensity, therefore, seismic assessment of structures should be based on probabilistic methods. Since PBSD (Performance‐based Seismic Design) philosophy was formulated, many researches have been conducted in this field in order to develop simple and accurate procedures for evaluating structural reliability. An important contribution has been provided by Jalayer and Cornell, who have developed a closed‐form expression to evaluate the mean annual frequency of exceeding a defined limit state. In this paper, by assuming the record‐to‐record variability as the only source of uncertainty, the seismic reliability of concentrically braced frames designed according to traditional and innovative methodologies is investigated, and a comparison between their performances is presented. In particular, two design methodologies have been applied: Eurocode 8 provisions and a new design methodology based on a rigorous application of ‘capacity design’ criteria. The innovative reduced section solution strategy, based on the reduction of cross sections at bracing member ends, has also been analysed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
106.
Paolo Boccotti Felice Arena Vincenzo Fiamma Alessandra Romolo Giuseppe Barbaro 《Ocean Engineering》2011,38(2-3):509-518
A method for obtaining the directional spectrum, on assuming that the frequencies of the elementary waves are all different from one another, is re-proposed in a form suitable for applications to sea states near a coast. The method is applied to an interval of 10 h during which the sea state remained basically steady state off the beach at Reggio Calabria (east coast of the Straits of Messina). It is shown that the directional spectrum converges as the length of the time series data grows. A numerical simulation of a 10 h sea state confirms that the directional spectrum converges as the length of the time series grows, and the convergence is onto the known directional spectrum used to make the numerical simulation. Through the numerical simulation, it is proved that the method, generally, is suitable for applications even with short time series of wind waves (duration of about 100Tp). Finally, it is shown that the method is not necessarily inadequate even with short records of multimodal sea states with different modal directions, modal amplitude ratios and intermodal distances. 相似文献
107.
We studied the stability of the restricted circular three-body problem. We introduced a model Hamiltonian in action-angle Delaunay variables. which is nearly-integrable with the perturbing parameter representing the mass ratio of the primaries. We performed a normal form reduction to remove the perturbation in the initial Hamiltonian to higher orders in the perturbing parameter. Next we applied a result on the Nekhoroshev theorem proved by Pöschel [13] to obtain the confinement in phase space of the action variables (related to the elliptic elements of the minor body) for an exponentially long time. As a concrete application. we selected the Sun-Ceres-Jupiter case, obtaining (after the proper normal form reduction) a stability result for a time comparable to the age of the solar system (i.e., 4.9 · 109 years) and for a mass ratio of the primaries less or equal than 10–6. 相似文献
108.
Alessandra Celletti Gabriella Pinzari 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):327-344
In the framework of the orbital determination methods, we study some properties related to the algorithms developed by Gauss, Laplace and Mossotti. In particular, we investigate the dependence of such methods upon the size of the intervals between successive observations, encompassing also the case of two nearby observations performed within the same night. Moreover we study the convergence of Gauss algorithm by computing the maximal eigenvalue of the jacobian matrix associated to the Gauss map. Applications to asteroids and Kuiper belt objects are considered. 相似文献
109.
110.
The problem of stability of the Lagrangian equilibrium point of the circular restricted problem of three bodies is investigated in the light of Nekhoroshev-like theory. Looking for stability over a time interval of the order of the estimated age of the universe, we find a physically relevant stability region. An application of the method to the Sun-Jupiter and the Earth-Moon systems is made. Moreover, we try to compare the size of our stability region with that of the region where the Trojan asteroids are actually found; the result in such case is negative, thus leaving open the problem of the stability of these asteroids. 相似文献